The invention relates to a multi-element ophthalmic lens system, and more particularly, to a method of and apparatus for a multi-element laminated ophthalmic lens system comprised of a rigid primary lens and at least one thin, pliable, additive lens having an initially non-mating curvature, pre-selected because of its radial difference and flexibly bonded thereto.
It is conventional in the prior art to produce individual ophthalmic lenses having both a spherical and a cylindrical correction. The power of such lenses is generally measured in diopters (D) which is the inverse of the focal length in meters. For example, the power of the human eye, including both the cornea and lens is about +60D. Spherical lenses are generally made with powers between -7.00D and +7.00D, usually in 0.25D steps. Cylindrical lenses are made in powers up to 4.00D, also in 0.25D increments. The necessary optical corrections for the aforesaid ophthalmic lens provide an enormous stocking problem in that each configuration must be available for a complete ophthalmic inventory. An inventory of ophthalmic lenses is generally provided in a large variety of spherical cylindrical and bifocal combinations. There are approximately one hundred and twenty spherical powers, thirty cylindrical powers, and 180.degree. of possible axial combinations which are conventionally prescribed by ophthalmic practitioners for eye glasses. Additionally, about twelve bifocal powers are generally utilized. The inventory requirements to provide immediate availability for any one of the aforesaid combinations is often times prohibitive. Therefore, the most often required lens configurations are stocked and the more seldom needed lens ordered from a lens manufacturer.
The conventional manner of fabrication of ophthalmic lenses generally includes the casting/grinding and polishing of single layer plastic or glass stock. Such fabrication techniques require expensive machinery, knowledgeable artisans and appropriate manufacturing facilities which are not readily available to individual ophthalmic practitioners. It may be seen that the complex curvatures required for combined spherical and cylindrical optic correction are accomplished by superimposing the curvature of one distinct lens onto another. Such techniques may be affected, by lens grinding machines which geometrically impose optical combinations onto a single lens blank. It is likewise possible to segregate the distinct optical patterns from one another in the lens manufacture, in that said optical patterns are initially segregated in the prescription.
The prior art has already recognized certain advantages to be gained from bonding together stock lenses for severe optical correction. One such method is shown and described in U.S. Pat. No. 4,070,105 issued to Marzouk. This reference sets forth the utilization of a Fresnel lens in a laminated configuration affording reduced thickness of the spectacle lens from what would otherwise be a relatively large spherical lens. Generally one member of the two element lens pair has a first index of refraction while a second element of the two element lens pair has a second index of refraction. By selecting the appropriate Fresnel lenses for the elements of a lens pair, each assembled lens may achieve the desired degree of spherical correction. This lens may also be made in a small laboratory without grinding or polishing.
The obvious advantage of incorporating a Fresnel lens in a laminated configuration is the provision of a thin lens assembly which affords the necessary optical correcting factors. The use of such Fresnel type lens correction has also been shown in U.S. Pat. Nos. 3,698,854 and 3,904,281, each issued to Jampolsky. In these prior art references, a thin, fully conformable, plastic membrane is applied and made to adhere with finger pressure to a conventional spectacle lens. The step quickly and permanently changes one or more optical characteristics of the spectacle lens to provide a change in the spectacle transmission across the field of view and/or the following: changing the light transmission to all colors by partial or entire occlusion with stenopaic slit, pin holes of uniform or varying size distributed either uniformly or stepwise or graded across the field, changing the light transmission either by uniform or graded diffusion, or a combination of each of the listed ways.
The subject prior art Fresnel type membrane may be embossed on one of its surfaces to form a Fresnel type lens or prism structure which introduces a deviation of the light ray for ophthalmic correction. Again the utilization of the Fresnel lens affords a distinct refractive power for ophthalmic correction in a lens assembly of reduced thickness. This construction has an additional light weight feature which benefits the user. Such a combination also reduces the manufacturing costs typical of conventional single layer lenses of the equivalent ophthalmic correction.
The use of the Fresnel membrane for ophthalmic correction is also set forth and shown in the Journal of the American Optometric Association, Volume 50, Number 9, 9-79. The use of the Fresnel lens laminated upon a monocular telescope system provides a telemicroscope which may also be known as a reading binocular. This reference reports the construction of such a telemicroscope utilizing plus lens Fresnel membranes as caps for the telemicroscopic systems. The advantages are multiple and include an easily constructed, inexpensive assembly with exceptional optical clarity.
The telemicroscope reference and the aforesaid ophthalmic Fresnel lens references clearly show the interest placed upon laminated lens construction by various prior art procedures. More conventional ophthalmic innovation in laminate lens construction also has surfaced for conventional ophthalmic lenses incorporating the combination for basic spherical, cylindrical and related corrections. More particularly, one laminate construction of two-ply lenses is shown in U.S. Pat. No. 1,948,636 issued to Tillyer. The lens assembly of the Tillyer patent teaches that a laminate lens construction may be provided by grinding adjacent surfaces of the laminate lenses into a mating configuration. The matingly curved surfaces are then cemented together in a non-conforming, non-flexible configuration. Such an assembly affords the advantages, however, of a laminate construction although the necessity of mating curvatures must be met.
A second prior art laminate lens construction is further set forth in U.S. Pat. No. 2,033,101 also issued to Tillyer et al. The second Tillyer patent discloses a laminate lens construction not requiring mating curvatures of bonded lenses. The lenses, however, are also not conformed to each other. In this embodiment, the lenses are cemented together along the circumferential periphery so as to seal the lens and the void therebetween. The individual lens laminates are thus rigid and structurally inflexible for facilitating circumferential bonding and the predetermined optical correction afforded by the pre-selected lens elements.
An additional prior art embodiment of a laminate lens construction is shown in U.S. Pat. No. 3,387,798 issued to Tolar. This patent teaches again pre-grinding of lenses to specific curvatures for mating. It is an object of the Tolar patent to provide a laminated, multi-focal lens assembly of improved appearance which is thin, light in weight, and strong. The laminated lens which is set forth in the Tolar patent again comprises structurally rigid, laminated lens elements. Each lens element is constructed with sufficient structural rigidity to maintain the specific mating curvature necessary for lamination. The laminate lens system set forth in Tolar then provides the ability to meet a myriad of ophthalmic corrections with a pre-selected inventory. The inventory of laminatable lenses is, however, by definition an inventory of lenses having pre-ground, mating surface curvatures and of sufficient structural rigidity to permit subsequent bonding to provide the aforedescribed thin, lightweight lens.
The inventory necessary for meeting the ophthalmic demands for laminate lens construction utilizing the above prior art approach is enormous. Although the laminate lens construction affords a myriad of benefits, the necessity for mating curvatures between bondable lenses necessitates an inventory of lens combinations which is often times not feasible. It would be an advantage, therefore, to provide a method and apparatus for an ophthalmic lens system utilizing an additive lens constructed of sufficiently thin, cross-section for flexibly conforming to any of a plurality of structural lenses. In this manner, the requisite inventory of mating lens combinations would be substantially reduced.
The present invention provides such a laminated lens system by providing a plurality of lens blanks having a series of cylindrical or spherical additive lens in graduated, radial differences for creating any given refractive power depending upon the lens curvature to which it is conformed and affixed. The flexible additive lenses of the present invention are constructed of a curvature specifically different from the curvature of the lens to which it will be bonded and are provided in graduated radial differences rather than ophthalmic powers in that the resulting ophthalmic power is determined by the specific radial difference as applied to the primary structural lens. Unlike the aforesaid prior art approaches, the present invention utilizes a thin, pliable lens which may be flexibly conformed to the structural lens, negating the need for structural rigidity in the additive lens and the necessity of pre-ground mating surfaces.